扫描指定package目录下的class（兼容jar包里的class）

import java.io.File;
import java.io.IOException;
import java.net.JarURLConnection;
import java.net.URL;
import java.util.*;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.logging.Logger;

public class PackageUtil {

    private final static Logger log = Logger.getLogger(PackageUtil.class.getName());

    /**
     * 扫描包目录下的类
     *
     * @param packageNames package names
     * @return list
     */
    public static List<Class<?>> scanClasses(String... packageNames) {
        // 存放扫描到的class
        Set<Class<?>> scannedClasses = new HashSet<>();
        // 存放扫过的资源文件，防止同样的包路径扫两遍
        Set<String> scannedResources = new HashSet<>();
        for (String packageName : packageNames) {
            String path = packageName.replace('.', '/');
            Enumeration<URL> resources;

            try {
                resources = Thread.currentThread().getContextClassLoader().getResources(path);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
            while (resources.hasMoreElements()) {
                URL resource = resources.nextElement();
                if (scannedResources.contains(resource.getFile()) || scannedResources.contains(resource.getFile() + "/")) {
                    continue;
                }
                scannedResources.add(resource.getFile());
                if (resource.getProtocol().equals("file")) {
                    scanClassesInClasspath(packageName, resource, scannedClasses);
                } else if (resource.getProtocol().equals("jar")) {
                    scanClassesInJar(packageName, resource, scannedClasses);
                }
            }
        }
        return new ArrayList<>(scannedClasses);
    }

    private static void scanClassesInClasspath(String packageName, URL resource, Set<Class<?>> scannedClasses) {
        File directory = new File(resource.getFile());
        if (directory.exists() && directory.list() != null) {
            for (String fileName : Objects.requireNonNull(directory.list())) {
                if (fileName.endsWith(".class")) {
                    String className = packageName + '.' + fileName.substring(0, fileName.length() - 6);
                    try {
                        scannedClasses.add(Class.forName(className));
                    } catch (ClassNotFoundException e) {
                        throw new RuntimeException(e);
                    }
                } else {
                    String subpackageName = packageName + '.' + fileName;
                    scannedClasses.addAll(scanClasses(subpackageName));
                }
            }
        }
    }

    private static void scanClassesInJar(String packageName, URL resource, Set<Class<?>> scannedClasses) {
        JarURLConnection jarURLConnection;
        JarFile jarFile;
        try {
            jarURLConnection = (JarURLConnection) resource.openConnection();
            jarFile = jarURLConnection.getJarFile();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        Enumeration<JarEntry> entries = jarFile.entries();
        while (entries.hasMoreElements()) {
            JarEntry entry = entries.nextElement();
            if (!entry.getName().endsWith(".class")
                    || entry.getName().endsWith("module-info.class")
                    || entry.getName().endsWith("package-info.class")
                    || !entry.getName().replace("/", ".").startsWith(packageName)
            ) {
                continue;
            }
            String className = entry.getName().substring(0, entry.getName().length() - 6).replace("/", ".");
            Class<?> clazz;
            try {
                clazz = Class.forName(className);
                if (clazz.getPackageName().startsWith(packageName)) {
                    scannedClasses.add(clazz);
                }
            } catch (Throwable e) {
                log.warning("扫描到class[%s]时异常，跳过此类。异常信息：%s".formatted(className, e.getMessage()));
            }
        }
    }


}